In the initial phase of this project, crotalase (a thrombin-like enzyme from eastern diamondback rattlesnake venom) has been purified and characterized. Amino acids involved in the active site are being identified by specific chemical modification and peptide separation and identification. Studies on the amino acid sequence of the enzyme are under way for comparison to the sequence of thrombin. Since crotalase is known to cleave peptide bonds in prothrombin as well as fibrinogen, we are investigating activity of the enzyme on blood clotting factors. These studies on the action of crotalase should help us obtain a better understanding of the possible clinical application of the enzyme. Since fibrin deposition is felt to be involved in burn trauma and since crotalase is known to produce a benign state of defibrinogenation, we are studying the application of crotalase to burn therapy using a rabbit model system. Blood coagulation may also be involved in tumor metastasis since it is believed that fibrin may be required for the adhesion of the tumor cells to vascular endothelium. Preliminary studies are underway to investigate the effects of crotalase induced defibrinogenation in known metastatic animal tumor model systems. A fibrinolytic enzyme has also been isolated from Crotalus atrox (western diamondback rattlesnake) and compared to crotalase. The fibrinolytic enzyme appears to be unique in its activity. Studies on its mechanism of fibrinolytic action of fibrinogen are presently underway.